Method for producing low carbon/oxygen conductive layers

ABSTRACT

The present invention provides a method for forming a substantially carbon- and oxygen-free conductive layer, wherein the layer can contain a metal and/or a metalloid material. According to the present invention, a substantially carbon- and oxygen-free conductive layer is formed in an oxidizing atmosphere in the presence of an organometallic catalyst using, for example, a chemical vapor deposition process. Such layers are particularly advantageous for use in memory devices, such as dynamic random access memory (DRAM) devices.

This is a division of application Ser. No. 09/146.297, filed Sep. 3,1998, now U.S. Pat. No. 6,284,655, which is incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to the preparation of semiconductor devicestructures. Particularly, the present invention pertains to methods offorming substantially carbon-free, and, optionally, oxygen-free,conductive layers using an organometallic catalyst.

BACKGROUND OF THE INVENTION

Chemical vapor deposition (hereinafter “CVD”) is defined as theformation of a non-volatile solid layer or film on a substrate by thereaction of vapor phase reactants that contain desired components. Thevapors are introduced into a reactor vessel or chamber, and decomposeand/or react at a heated surface on a wafer to form the desired layer.CVD is but one process of forming relatively thin layers onsemiconductor wafers, such as layers of elemental metals or compounds.It is a favored layer formation process primarily because of its abilityto provide highly conformal layers even within deep contacts and otheropenings.

For example, a compound, typically a heat decomposable volatile compound(also known as a precursor), is delivered to a substrate surface in thevapor phase. The precursor is contacted with a surface which has beenheated to a temperature above the decomposition temperature of theprecursor. A coating or layer forms on the surface. The layer generallycontains a metal, metalloid, alloy, or mixtures thereof, depending uponthe type of precursor and deposition conditions employed.

Precursors typically utilized in CVD are generally organometalliccompounds, wherein a hydrocarbon portion of the precursor functions asthe carrier for the metal or metalloid portion of the precursor duringvaporization of the liquid precursor. For microelectronic applications,it is often desirable to deposit layers having high conductivity, whichgenerally means that the layers should contain minimal carbon and oxygencontaminants. However, one problem of a CVD deposited layer formed froman organometallic precursor is incorporation of residual carbon from thehydrocarbon portion of the precursor and oxygen that may be present inthe atmosphere during deposition. For example, oxygen incorporation intothe layer before or after deposition generally results in higherresistivity. Further, it is also believed that organic incorporation(such as pure carbon or hydrocarbon) into the resultant layer reducesdensity and conductivity. A low density layer can subsequently lead tooxygen incorporation into the layer when it is exposed to ambient air.

Conductive layers formed by CVD processing can be used in thefabrication of various integrated circuits. For example, capacitors arethe basic energy storage components in storage cells of memory devices,such as dynamic random access memory (DRAM) devices, static randomaccess memory (SRAM) devices, and even in ferroelectric memory (FE)devices. As memory devices become more dense, it is necessary todecrease the size of circuit components. One way to retain storagecapacity of memory devices and decrease its size is to increase thedielectric constant of the dielectric layer of the capacitor component.Such components typically consist of two conductive electrodes insulatedfrom each other by a dielectric material. In order to retain storagecapacity and to decrease the size of memory devices, materials having arelatively high dielectric constant can be used as the dielectric layerof a storage cell. Materials having relatively high dielectric constantsare generally formed on a device surface as thin layers. Generally, highquality thin layers of metals and conductive metal oxides, nitrides, andsilicides, are used as electrode materials for storage cell capacitors.To be effective electrodes, low resistivity is desired. Therefore,layers having low carbon and/or oxygen content are desired. Further,various applications also require such low resistivity conductivelayers, e.g., contacts, interconnects, etc. In addition, the presence ofcarbon in an electrode layer may “poison” the dielectric layer thus,reducing the effectiveness of the capacitor.

SUMMARY OF THE INVENTION

Thus, what is yet needed are methods for forming substantially carbon-and oxygen-free conductive layers useful for semiconductor structures,that can be used in microelectronic devices, such as memory devices. Forexample, a substantially carbon- and oxygen-free layer is desirable whena conductive material, e.g., ruthenium, is used as a conductive layer.In general, such a conductive layer preferably contains unoxidized orrelatively minor amounts of oxidized metal or metalloid which, in largeamounts, can adversely affect its characteristics. Further, conductivelayers containing relatively large amounts of carbon and/or oxygen donot provide adequate conductivity characteristics.

Advantageously, the present invention provides a method for forming asubstantially carbon-free and, optionally, oxygen-free layer including ametal- or metalloid containing material. Preferably, a method accordingto the present invention includes forming a layer in the presence of anorganometallic catalyst. The present invention also provides asubstantially carbon-free and, optionally, a substantially oxygen-freeconductive layer that can be used as a barrier layer, and/or an adhesionlayer, on an electrode, or any other conductive layer in an integratedcircuit structure, such as in a capacitor of a memory device.

A method according to the present invention is particularly well suitedfor forming layers on a surface of a semiconductor substrate orsubstrate assembly, such as a silicon wafer, with or without layers orstructures formed thereon, used in forming integrated circuits. It is tobe understood that a method according to the present invention is not tobe limited to layer formation on silicon wafers; rather, other types ofwafers (e.g., gallium arsenide wafer, etc.) can be used as well. Amethod according to the present invention can also be used insilicon-on-insulator technology. The layers can be formed directly onthe lowest semiconductor surface of the substrate, or they can be formedon any of a variety of layers (i.e., surfaces) as in a patterned wafer,for example. Thus, the term “semiconductor substrate” refers herein to abase semiconductor layer, e.g., the lowest layer of silicon material ina wafer or a silicon layer deposited on another material such as siliconor sapphire. The term “semiconductor substrate assembly” refers hereinto a semiconductor substrate or a substrate having one or more layers orstructures formed thereon.

Accordingly, one aspect of the present invention provides a method foruse in fabrication of integrated circuits. Preferably, the methodincludes the steps of forming a substrate assembly having a surface andforming a substantially carbon- and oxygen-free layer from a precursorcomprising a conductive material in an oxidizing atmosphere and in thepresence of an organometallic catalyst. A metal portion of theorganometallic catalyst is preferably different than the conductivematerial of the precursor.

As used herein, “substantially carbon-free” refers to an amount ofcarbon present in a layer that is preferably about 1.0% by atomicpercent or less, more preferably about 0.1% by atomic percent or less,and most preferably about 0.05% by atomic percent or less. If used,“substantially oxygen-free” refers to an amount of oxygen present in alayer that is preferably about 1.0% by atomic or less, more preferablyabout 0.5% by atomic or less, and most preferably about 0.1% by atomicor less.

Preferably, the metal portion of the organometallic catalyst is selectedfrom the group consisting essentially of platinum, paladium, rhodium,and iridium and the material is selected from the group consistingessentially of a metal, a metalloid, and mixtures thereof. The metal andthe metalloid can each be in the form of a sulfide, a selenide, atelluride, a nitride, a silicide, an oxide, and mixtures thereof. Thematerial is preferably selected from the group consisting essentially oftitanium, tantalum, ruthenium, osmium, iron, rhodium, cobalt, nickel,iridium, cerium, tungsten, aluminum, copper, and mixtures thereof.

Additionally, the method of the present invention provides that thesubstantially carbon- and oxygen-free layer can further include a metalselected from the group consisting essentially of platinum, paladium,rhodium, and iridium. Preferably, the metal portion from theorganometallic catalyst included in the substantially carbon- andoxygen-free layer is in an amount no greater than about 20% by atomicpercent.

Preferably, the step of forming the substantially carbon- andoxygen-free conductive layer includes depositing a precursor by chemicalvapor deposition in the presence of a platinum-containing organometalliccatalyst. More preferably, the precursor includes a material selectedfrom the group consisting essentially of titanium, tantalum, ruthenium,osmium, iron, rhodium, cobalt, nickel, iridium, cerium, tungsten,aluminum, copper, and mixtures thereof.

Another aspect of the present invention provides a method for use information of a capacitor. Preferably, the method includes the steps offorming a surface of a substrate assembly and forming a first electrodeon at least a portion of the surface of the substrate assembly.Preferably, the first electrode includes a substantially carbon- andoxygen-free layer deposited in an oxidizing atmosphere in the presenceof an organometallic catalyst, wherein the substantially carbon- andoxygen-free layer is formed from a conductive metal-containingprecursor, wherein the conductive metal of the precursor is not the sameas a metal portion of the organometallic catalyst. The method alsoincludes the steps of forming a dielectric material over at least aportion of the first electrode; and forming a second electrode on atleast a portion of the dielectric material.

Preferably, the step of forming the substantially carbon- andoxygen-free conductive layer includes forming a substantially carbon-and oxygen-free layer by chemical vapor deposition. The substantiallycarbon- and oxygen-free conductive layer may also be a substantiallycarbon- and oxygen-free conductive barrier layer.

Yet another aspect of the present invention provides a semiconductorstructure. Typically, the semiconductor structure includes a substrateassembly including a surface and a substantially carbon- and oxygen-freeconductive layer comprising a major portion of a conductive material anda minor portion of a metal selected from the group consistingessentially of platinum, paladium, rhodium, and iridium, wherein themajor portion of the conductive material is not the same as the minorportion of the metal. Preferably, the minor portion comprises about 20%by atomic percent or less of the substantially carbon- and oxygen-freeconductive layer.

The substantially carbon- and oxygen-free conductive layer preferablyincludes a material selected from the group consisting essentially oftitanium, tantalum, ruthenium, osmium, iron, rhodium, cobalt, nickel,iridium, cerium, tungsten, aluminum, copper, and mixtures thereof. Thus,in the semiconductor structure of the present invention, thesubstantially carbon- and oxygen-free conductive layer may be at leastone of a semiconductor structure selected from the group consistingessentially of an electrode layer, an electrode, a barrier layer, acontact layer, an interconnect component, and an adhesion layer.

A further aspect of the present invention provides a semiconductorstructure that typically includes a substrate assembly including asurface and a substantially carbon-free conductive layer comprising amajor portion of a conductive metal oxide and a minor platinum portion.Preferably, the minor platinum portion comprises about 20% by atomicpercent or less of platinum in the substantially carbon-free conductivelayer.

The substantially carbon- free conductive layer may include a majorportion of a metal oxide selected from the group consisting essentiallyof aluminum oxide, titanium oxide, tungsten oxide, ruthenium oxide,osmium oxide, iridium oxide, rhodium oxide, tantalum oxide, cobaltoxide, copper oxide, and mixtures thereof.

Yet a further aspect of the present invention provides a memory cellstructure including a substrate assembly including at least one activedevice and a capacitor formed relative to the at least one activedevice. The capacitor comprises at least one electrode including asubstantially carbon- and oxygen-free conductive layer, wherein thesubstantially carbon- and oxygen-free conductive layer comprises a majorportion of a conductive material selected from the group consistingessentially of titanium, tantalum, ruthenium, osmium, iron, rhodium,cobalt, nickel, iridium, cerium, tungsten, aluminum, copper, andmixtures thereof; and a minor portion of a metal selected from the groupconsisting essentially of platinum and paladium.

The capacitor may further include a first electrode formed on asilicon-containing region of the at least one active device; adielectric material on at least a portion of the first electrode; and asecond electrode on the high dielectric material, wherein the firstelectrode comprises the substantially carbon- and oxygen-free conductivelayer. The substantially carbon and oxygen-free conductive layer may beat least one of a semiconductor structure selected from the groupconsisting essentially of an electrode layer, an electrode, a barrierlayer, a contact layer, an interconnect component, and a bond pad.

Another aspect of the present invention provides a method for forming asubstantially carbon- and oxygen-free conductive layer. Preferably, themethod includes forming a substrate assembly including a heated surface;forming a reactor chamber having an oxidizing atmosphere within thechamber; supplying a precursor to the reactor; and supplying anorganometallic catalyst to the reactor. Preferably, the substantiallycarbon- and oxygen-free conductive layer forms on the heated surface.The oxidizing atmosphere may include a compound selected from the groupconsisting essentially of oxygen, ozone, nitrous oxide, hydrogenperoxide, R₂O₂, and a combination thereof, wherein R is selected fromthe group consisting of a saturated or unsaturated linear, branched orcyclic hydrocarbon group having about 1 carbon atom to about 20 carbonatoms, preferably about 2 carbon atoms to about 12 carbon atoms, forexample, methyl, ethyl, isopropyl, t-butyl, heptyl, dodecyl, octadecyl,amyl, 2-ethylhexyl, and the like. Preferably, the reaction chamber is ata pressure of about 0.5 torr to about 50 torr.

The method of the present invention may also include the step ofsupplying a reactive gas to the reactor, wherein the reactive gas isselected from the group consisting essentially of nitrogen-containinggases, silane, hydrogen sulfide, and mixtures thereof.

Another aspect of the present invention provides a method of optimizingcomponents in a conductive layer. Preferably, the method includes thestep of forming a conductive layer, wherein forming the conductive layerincludes forming a reactor chamber having a known concentration ofoxygen in an oxidizing atmosphere; forming a substrate having a heatedsurface; supplying a fixed amount of a precursor to a reactor; andsupplying a fixed amount of an organometallic catalyst to the reactor.The method also includes the step of analyzing the conductive layer forcomponent amounts. The steps of forming and analyzing a conductive layercan be repeated, wherein one of the fixed amount of the organometalliccatalyst or the concentration of oxygen in the oxidizing atmosphere isvaried until carbon is detected in the conductive layer.

Preferably, the fixed amount of the organometallic catalyst is about 15%by atomic percent and is varied by decreasing the fixed amount.Additionally, and preferably, the known concentration of oxygen in theoxidizing atmosphere is about 30% by atomic percent and is varied bydecreasing the known amount. The amount of organometallic catalyst canbe optimized empirically such that the amount of catalyst can be reduceduntil carbon is detected in the layer formed.

These and other objects, features and advantages of the presentinvention will be apparent from the following description of variousembodiments and as illustrated in the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional schematic of one embodiment of a structureincluding a layer formed in accordance with the present invention.

FIG. 2 is a cross-sectional schematic of another embodiment of acapacitor including a layer formed in accordance with the presentinvention.

FIG. 3 is a cross-sectional schematic of an alternate embodiment of alayer formed in accordance with the present invention.

FIG. 4 is a depth profile of a layer formed in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention provides a method for forming a conductive layerthat contains substantially no carbon and, optionally, no oxygen usingan organometallic catalyst. Preferably, the method includes forming asubstantially carbon- and oxygen-free conductive layer from-a precursorin the presence of an organometallic catalyst. The resultantsubstantially carbon- and oxygen-free layer can be a metal, a metalloid,and mixtures thereof. Each of the metal and the metalloid can be in theform of a sulfide, a nitride, a selenide, a telluride, a nitride, asilicide, an oxide, mixtures thereof. Preferably, the substantiallycarbon- and oxygen-free conductive layer formed is a metal layer. Thelayer can be deposited in a wide variety of thicknesses, depending uponthe desired use. Preferably, the substantially carbon- and oxygen-freelayer is a conductive layer that can be used in memory devices, such asDRAM devices.

A. Layer Formation Method

The present invention broadly relates to the formation of asubstantially carbon-free and, optionally, a substantially oxygen-freelayer. In the present invention, one preferred system for forming alayer is chemical vapor deposition (CVD). CVD is generally a process inwhich a layer is deposited by a chemical reaction or decomposition of agas mixture at elevated temperature at a substrate surface or in itsvicinity. CVD can be classified into various types in accordance withthe heating method, gas pressure, and/or chemical reaction. For example,conventional CVD methods include: (a) cold wall type CVD, in which onlya deposition substrate is heated; (b) hot wall type CVD, in which anentire reaction chamber is heated; (c) atmospheric CVD, in whichreaction occurs at a pressure of about one atmosphere; (d) low-pressureCVD in which reaction occurs at pressures from about 10⁻¹ to 100 torr;(c) electron-beam assisted CVD and ion-beam assisted CVD in which theenergy from an electron-beam or an ion-beam directed towards thesubstrate provides the energy for decomposition of the precursor; (f)plasma assisted CVD and photo-assisted CVD in which the energy from aplasma or a light source activates the precursor to allow depositions atreduced substrate temperatures; and (g) laser assisted CVD wherein laserlight is used to heat the substrate or to effect photolytic reactions inthe precursor gas. In the cold wall type CVD, heating of substrates in aCVD reactor may be accomplished by several method including the use ofhot stages or induction heating.

Broadly, thermal CVD includes any type of apparatus in which thesubstrates and/or the gaseous precursor is heated and could includestandard thermal reactors such as cold wall/hot substrates reactors andhot wall type reactors, as well as radiation beam reactors in which abeam (such as a laser beam) is used to heat the substrate and/or todecompose gaseous precursor.

In a typical CVD process, a substrate on which deposition is to occur isplaced in a reaction chamber, and is heated to a temperature sufficientto cause the decomposition of vapors of the precursor, as describedbelow. When these vapors are introduced into the reaction chamber andtransported to the vicinity of the substrate, they will decomposethereon to deposit a layer containing a metal or metalloid.

For example, in a thermal reactor CVD system it is preferable that thedecomposition reaction occur at the substrate, and for this reason it ispreferable to heat the substrate to a temperature in excess of thedecomposition temperature of the precursor. Similarly, in a radiationbeam induced CVD technique, the radiation (such as an ion beam) ispreferably used to heat the substrate so that decomposition of theprecursor occurs as the substrate.

These CVD processes can be used to provide blanket deposition of metalor metalloid layers on substrates. These layers can then be patterned byconventional lithography methods, if desired. Additionally, selectedarea depositions may be accomplished by energy beam assisted CVD where abeam of energy, such as an ion beam, selectively heats small portions ofthe substrate.

Any CVD apparatus design may be used in the present invention includinghot wall reactors, cold wall reactors, radiation beam assisted reactors,plasma assisted reactors, and the like. For blanket depositions, a coldwall-hot substrate reactor may sometimes be preferred as this design isefficient in regards to precursor consumption. For selected areadepositions, a radiation beam assisted reactor may be preferred as theradiation beam may be used to “write” metal containing layers onto smallareas of the substrate.

In the present invention, a method for forming a substantially carbon-and oxygen-free metal- or metalloid-containing layer is preferablyconducted using a CVD process in the presence of an organometalliccatalyst. Preferably the method is carried out in the presence of anoxidation gas, and under a dynamic vacuum of about 0.5 to 50 torr in astandard cold-wall, CVD reactor chamber. Typically, a precursor iscontained in a precursor bubbler, that is typically heated, at one endof the reactor and is exposed to a vacuum by flowing an inert carriergas through the heated bubbler to vaporize the precursor. Additionally,an organometallic catalyst is contained in a catalyst bubbler, that istypically heated, in proximity to the precursor reservoir. Theorganometallic catalyst is carried to a vacuum by flowing a carrier gasthrough the heated bubbler which vaporizes the organometallic catalyst.Preferably, vaporization of the precursor and the organometalliccatalyst is accomplished substantially simultaneously. The vacuum can beprovided by a suitable vacuum pump positioned at the opposite end ofreaction chamber. The precursor vapor and organometallic catalyst vaporeach then pass into a reaction chamber that contains one or more unitsof the substrate. The substrate, e.g., wafers, are preferably held in avertical or a horizontal position by a suitable holder. The reactionchamber is maintained at a preselected temperature, by means of anexternal furnace or an internal heater chuck, which is effective todecompose the precursor vapor and the organometallic catalyst vapor soas to deposit a layer on the exposed surfaces of the substrate units.Preferably, the reaction chamber is maintained at about 150° C.-700° C.,more preferably at about 200° C.-500° C., during the deposition process.

Generally, vacuum systems are used for CVD of the metal or metalloids.There is a wide range of operation conditions with respect to thepressure in the system, operating pressures of 1 to 100 mtorr have beenused in the absence of carrier gas and higher or lower pressures arealso acceptable, i.e., up to about 10 torr. These pressures are largelydetermined by the pumping speed of the vacuum equipment, the chambervolume, the vapor pressure of the precursor and the vapor pressure ofthe organometallic catalyst. Optionally, a carrier gas can be added toincrease the total pressure, which is passed through or over a solid orliquid precursor. The pressure used is typically optimized to yield themaximum conformation or growth rate.

However, it is preferred to conduct the method of the present inventionin the presence of an oxidizing atmosphere, more preferably in thepresence of an oxidation gas, such as an oxygen-containing gas.Preferred oxidizing atmospheres may include a compound selected from thegroup consisting essentially of oxygen, ozone, nitrous oxide, hydrogenperoxide, R₂O₂, and a combination thereof, wherein R is selected fromthe group consisting of a saturated or unsaturated linear, branched orcyclic hydrocarbon group having about 1 carbon atom to about 20 carbonatoms, preferably about 2 carbon atoms to about 12 carbon atoms, forexample, methyl, ethyl, isopropyl, t-butyl, heptyl, dodecyl, octadecyl,amyl, 2-ethylhexyl, and the like. A carrier gas may also be used and istypically bubbled through the precursor and the organometallic catalystduring vaporization. Preferably, the carrier gas is a non-oxidizing gas,such as helium, argon, nitrogen, neon, krypton, xenon, and mixturesthereof. Additionally, a reactive gas may also be used, which isselected from the group consisting essentially of a nitrogen-containinggas (such as ammonia), silane, hydrogen suflide, and mixtures thereof,depending upon the desired characteristics of the resulting layer.Accordingly, an optional gas is preferably selected from the groupconsisting essentially of a carrier gas, a reactive gas, and mixturesthereof. When carrier gases are used, pressures may range from about 0.1torr to about 760 torr (atmospheric pressure) and are more typically inrange of 0.5 to 300 torr, with the pressure chosen to yield the bestconformation and a reasonable growth rate.

The precursor and the organometallic catalyst are generally maintainedat a constant temperature during the vaporization process for ease ofhandling. The temperature is necessarily below the respectivedecomposition temperature, but at a temperature such that it issufficiently capable of being volatilized in the process of chemicalvapor deposition.

Prior to initiating CVD, the substrates, such as silicon wafers arepre-cleaned by the standard means of sequential soaking in baths such astetrachloroethane, methanol, distilled water, dilute hydrofluoric acid,and distilled water, for example. The wafers are placed in the CVDreaction chamber. The temperature is typically about at least as high asthe melting point of the precursor and the organometallic catalyst, sothat the precursor and the organometallic catalyst,each vaporize and thewafer surface is exposed to the vapors of for a time sufficient toproduce a layer, typically about 1 minute or less.

Generally, a layer so formed has a thickness of about 200 angstroms toabout 500 angstroms, although the thickness of the layers may be alteredby the time of exposure to the vapors, depending upon the desired use ofthe layer. The layers so formed are generally smooth and highlyreflective upon visual inspection. Surprisingly, a resulting conductivelayer is formed on the substrate surface (including metals or metalloidsfrom the precursor) that is substantially carbon- and oxygen-free whenformation takes place in the presence of an organometallic catalyst.This is true even when the formation of the layer occurs in an oxidizingatmosphere. However, in some instances, it may be advantageous to form alayer that includes some amount of carbon and/or oxygen. Accordingly, itis within the scope of the present invention to provide a method that isadaptable to form conductive layers that contain some amounts of carbonand/or oxygen. This can be accomplished by varying the amount oforganometallic catalyst, concentration of oxygen in the oxidizingatmosphere, or both.

When a layer containing residual catalyst material is desired, themethod of the present invention can be optimized by varying the amountof organometallic catalyst, oxidizer, or both that are added to the CVDreactor. For example, a known ratio of organometallic catalyst toprecursor can be added to the reactor and the amount of oxidizer can bedecreased. After deposition, substrates can be analyzed using aconventional surface analytical technique such as by x-ray photoelectron spectroscopy (XPS) or Auger electron spectroscopy (AES) methodsto generate a depth profile. Subsequent deposition reactions can beperformed by sequentially decreasing the amount of organometalliccatalyst and the oxidizer can be decreased to the point where carbon isobserved. The oxidizer typically has a flow rate of about 50 sccm andcan be decreased to as low as about 1 sccm. Layers so formed can beanalyzed as above for the presence of carbon and/or oxygen. By utilizingthis optimization scheme, layer formation conditions can be determinedwhen different conductive metal- or metalloid-containing precursors areused, when it is desirable to minimize catalyst material in the layer,and when it is desirable to adjust layer thickness.

When a substantially carbon- and oxygen-free layer is desired, theorganometallic catalyst is utilized in a minor amount, preferably thelayer includes about 15% by atomic percent or less of a metal from theorganometallic catalyst, more preferably about 10% by atomic percent orless, and more preferably about 5% by atomic percent or less. Byexample, when a layer is desired that contains about 5% by atomicpercent of catalyst material, the optimization scheme typically beginswith an initial input of an organometallic catalyst amount of about 5%catalyst carrier flow to the precursor carrier flow.

B. Organometallic Catalyst

As discussed above, layer formation in accordance with the presentinvention is preferably accomplished in the presence of anorganometallic catalyst. “Organometallic catalyst,” as used herein,means a mononuclear (i.e., monomer) compound having an organic portionand a metallic portion.

As used herein, “organic portion” means a hydrocarbon group that isclassified as an aliphatic group, cyclic group, or a combination ofaliphatic and cyclic groups (e.g., alkaryl and aralkyl groups). In thecontext of the present invention, the term “aliphatic group” means asaturated or unsaturated linear or branched hydrocarbon group. This termis used to encompass alkyl, alkenyl, and alkynyl groups, for example.The term “alkyl group” means a saturated linear or branched hydrocarbongroup, including, for example, methyl, ethyl, isopropyl, t-butyl,heptyl, dodecyl, octadecyl, amyl, 2-ethylhexyl, and the like. The term“alkenyl group” means an unsaturated linear or branched hydrocarbongroup with one or more carbon-carbon double bonds, such as a vinylgroup. The term “alkynyl group” means an unsaturated linear or branchedhydrocarbon group with one or more triple bonds. The term “cyclic group”means a closed ring hydrocarbon group that is classified as an alicyclicgroup, aromatic group, or heterocyclic group. The term “alicyclic group”means a cyclic hydrocarbon group having properties resembling those ofaliphatic groups. The term “aromatic group” or “aryl group” means amono- or polynuclear aromatic hydrocarbon group. The term “heterocyclicgroup” means a closed ring hydrocarbon in which one or more of the atomsin the ring is an element other than carbon (e.g., nitrogen, oxygen,sulfur, etc.).

The term “group” is used to describe a chemical substituent thatincludes the unsubstituted group and the group with nonperoxidic O, N,or S atoms, for example, in the chain as well as carbonyl groups orother conventional substitution. For example, the phrase “alkyl group”is intended to include not only pure open chain saturated hydrocarbonalkyl substituents, such as methyl, ethyl, propyl, t-butyl, and thelike, but also alkyl substituents bearing further substituents known inthe art, such as hydroxy, alkoxy, alkylsulfonyl, halogen atoms, cyano,nitro, amino, carboxyl, etc. Thus, “alkyl group” includes ether groups,haloalkyls, nitroalkyls, carboxylalkyls, hydroxylalkyls, sulfoalkyls,etc.

The metal portion of the organometallic catalyst is preferably selectedfrom the group consisting essentially of platinum, paladium, rhodium,and iridium. While not wishing to be bound by any particular theory, itis believed that the metal portion of the organometallic catalystcompetitively reacts with the oxidizer to promote the combustion of theorganic component of the precursor. A preferable organometallic catalystis selected from the group consisting essentially of MeCpPtMe₃ (whereCp=cyclopentadienyl), CpPtMe₃, Pt(acetylacetonate)₂, Pt(PF₃)₄, andPt(CO)₂Cl₂.

C. Precursors

Various combinations of compounds described herein can be used in theprecursor for chemical vapor deposition. Thus, as used herein, a“precursor” refers to a liquid or solid that includes one or morecompounds of the type described herein. The precursor can also includeone or more organic solvents suitable for use in chemical vapordeposition, as well as other additives. Preferably, substantiallycarbon-free and, optionally, substantially oxygen-free layers containmetal or metalloid materials formed from a precursor. A preferredprecursor typically contains an organic portion, as defined above, and ametal or metalloid portion, preferably wherein the metal or metalloid ofthe precursor is not the same as the metal in the organometalliccatalyst. In metal- or metalloid-complexes useful as precursors,substitution in the organic portion is often tolerated and is sometimesadvisable. Thus, substitution is anticipated in precursors useful in thepresent invention.

As mentioned above, substantially carbon- and oxygen-free layers formedin accordance with the present invention are preferably conductive, andmore preferably include a metal or a metalloid. Suitable metal ormetalloid materials for forming a conductive layer can be selected fromthe group consisting essentially of titanium, tantalum, ruthenium,osmium, iron, rhodium, cobalt, nickel, iridium, cerium, tungsten,aluminum, copper, and mixtures thereof. These materials may also be theoxide form thereof. Advantageously, the method according to the presentinvention may be utilized to tailor the oxygen content in the oxide formof these materials. This is particularly desirable for use in formingmetal oxide films that are essentially carbon-free.

Thus, suitable precursors for forming a conductive film or layer havingan organic portion and a metal or metalloid portion in the presentinvention include, for example, substituted ruthenoscenes andosmoscenes. Suitable precursors can have the formula L_(y)RuX₂, whereinis a neutral or monoanionic ligand selected from the group consistingessentially of linear hydrocarbyls, branched hydrocarbyls, cyclichydrocarbyls, cyclic alkenes, dienes, cyclic dienes, bicyclic dienes,trienes, cyclic trienes, bicyclic alkenes, bicyclic dienes, bicyclictrienes, tricyclic alkenes, tricyclic dienes, tricyclic trienes,fluorinated derivatives thereof, combinations thereof, and derivativesthereof additionally containing heteroatoms such as a halide, Si, S, Se,P, As, N or O; y has a value from one to three; X is a pi-bonding ligandselected from the group consisting essentially of CO, NO, CN, CS,nitrites, isonitriles, trialkylphosphine, trialkylamine, isocyanide, andcombinations thereof, and z has a value from 1 to three, as described inApplicant's Assignee's copending patent application Ser. No. 09/141,236,entitled “Precursor Chemistries for Chemical Vapor Deposition ofRuthenium and Ruthenium Oxide.” Other suitable precursors can have theformula (diene)Ru(CO)₃, wherein “diene” refers to linear, branched, orcyclic dienes, bicyclic dienes, tricyclic dienes, fluorinatedderivatives thereof, combinations thereof, and derivatives thereofadditionally containing heteroatoms such as halide, Si, S, Se, P, As, Nor O as described in copending U.S. Ser. No. 09/140,878, dated Aug. 27,1998. These precursors can be prepared according to the methodsdescribed in the above-referenced patent applications or according tothe methods described in copending U.S. Pat. Ser. No. 09/141,431, datedAug. 27, 1998, entitled “Methods for Preparing Ruthenium and OsmiumCompounds.” Other suitable precursors can have the formulae (1) (CO)₄MLor (2) M₂[μ-(η²:η⁴-C₄R₄](CO)₆, wherein M is iron, ruthenium, or osmiumin formula (1) and L is a two-electron donor ligand and each R is H,halo, OH, alkyl, perfluoroalkyl, or aryl, as described in U.S. Pat. No.5,376,849 (McCormick et al.). Prefered precursors can be selected fromthe group of (cyclohcxadiene)Ru(CO)₃, (cycloheptadiene)Ru(CO)₃,bis(isoproplylcyclopentadienyl)ruthenium,bis(isoproplycyclopentadienyl)osmium; osmium tetrachloride;tris(acetylacentonate)ruthenium; ruthenium carbonyl chloride; andpenta(trifluorophosphine)ruthenium.

Conductive barrier layer formation is also possible in accordance withthe present invention. Because metal nitrides are particularly useful asbarrier films or layers, suitable precursors would betetrakis-(diethylamino)-titanium, tetrakis-(dimethylamino)-titanium,ethylimido tantalum, terbutylimido-tris-dimethylamino tantalum, and(isopropylcyclopentadienyl)₂WH₂, that are capable of forming layerscontaining a nitride form of titanium, tantalum, and tungsten, dependingon the precursor used.

D. Substrate Assemblies

Any type of substrate can be used, including metals, graphite,semiconductors, insulators, ceramics and the like as long as thesubstrate is not substantially deteriorated under the depositionconditions. Such substrates include, but are not limited to, silicon,tin oxide, gallium arsenide (GaAs), silica, glass, alumina, zirconia, aswell as polyimide, polymethyl-methacrylate, polystryene, parylene, andother synthetic polymers.

Although the exemplified substrate surfaces are planar, the presentprocess can provide conformal deposition so that the material can bedeposited as continuous layers into recesses, trenches, and vias, andover stepped surfaces, such as those which are topologicallymicrostructured including those that may have relatively high aspectratios. The substrate can be of any desired shape, either regular orirregular. Thus, the substrate can be a rectangular solid or other solidcharacterized by flat exterior surfaces. Cylindrical surfaces, such asrods and wires, can also be coated according to this invention.Spherical surfaces and other curved surfaces can also be coated. Thesubstrate can even be particulate and/or be hollow, as for example, atube or a hollow or porous sphere or irregular particle having openingsto the exterior. For example, such applications include capacitors suchas planar cells, trench cells (e.g., double sidewall trench capacitors),stacked cells (e.g., crown, V-cell, delta cell, multi-fingered, orcylindrical container stacked capacitors), as well as field effecttransistor devices. The substrate could also include rough surfaces,such as hemispherical grain polysilicon.

Referring to FIG. 1, a layer 34 is shown deposited on a substrateassembly 31, including one or more layers 30, 32. The layer 34,deposited in accordance with the present invention, includes a metal ormetalloid material, which depends upon the composition of the precursorused, and a metal, dependent upon the composition of the organometalliccatalyst used. Preferably, the layer 34 is substantially carbon- andoxygen-free. Accordingly, the layer 34 can be thought of as an alloyformed from the metal or metalloid material from the precursor and themetal from the organometallic catalyst. As mentioned above, the layer 34can also contain minor amounts of carbon and/or oxygen, depending uponthe layer forming conditions utilized. Preferably, the layer has athickness of about 100 angstroms to about 500 angstroms.

Referring to FIG. 2, a cross-sectional view of a portion of a dynamicrandom access memory (DRAM) cell is shown illustrating the use of thepresent invention. Typically, a silicon substrate 7 has at least onesubstantially planar field oxide region 5 formed thereon (generallyformed by conventional local oxidation of silicon (LOCOS) or specialLOCOS processing). The creation of the field oxide region 5 is precededor followed by a thermally grown dielectric layer 8, typically ofsilicon oxide. Following the creation of the field oxide region 5 andthe dielectric layer 8, a first conductively doped polysilicon layer 10,a metal silicide layer 15, an oxide layer 16, and a relatively thicknitride layer 20 are deposited. The layers are patterned and etched toform wordlines 21 and N-channel (NCH) field effect transistors 22. Theformation of the FETs 22 and wordlines 21 as described are exemplary toone application to be used in conjunction with the present embodiment ofthe invention. Other methods of fabrication and other applications arealso feasible and perhaps equally desirable.

Next, a relatively thick first insulative conformal layer of undopedoxide 40 is blanket deposited to fill the storage node areas and overliethe FETs 22 and wordlines 21. The oxide 40 is planarized, for example bychemical mechanical planarization (CMP), in order to provide a uniformheight. Optionally nitride, oxynitride or another suitable material maybe deposited as the insulative layer.

The oxide 40 is etched, preferably dry etched, to form self-alignedopenings (not labeled) exposing the contact area 55 of the substrate. Inorder to provide electrical communication between the substrate 7 and astorage cell capacitor 89, a polysilicon plug 65 is formed in eachopening. Various methods may be used to form the polysilicon plugs 65,such as a selective silicon growth from the contact area 55 or anin-situ doped polysilicon deposition and subsequent etch back or CMPback. Upper portions of each polysilicon plug 65 is removed during a dryetch in order to form a recess (not labeled). Optionally, a titaniumsilicide layer 67 overlies the polysilicon plug 65, which provides afirst barrier layer.

A second barrier layer 75 is formed by a chemical vapor deposition(CVD), as described above. The barrier layer 75 typically has athickness that is equal to or greater than the depth of the recess inthe oxide layer 40. In general, the titanium silicide layer 67 lowers acontact resistance between the polysicilon plug 65 and the barrier layer75 which tends to reduce degradation during subsequent processing. Thebarrier layer 75 tends to prevent diffusion of silicon from thepolysilicon plug 65 and the titanium silicide layer 67 during subsequenthigh temperature anneals. Preferably, the barrier layer 75 contains aconductive metal selected from the group consisting essentially ofaluminum, titanium, tungsten, ruthenium, osmium, iridium, rhodium, andmixtures thereof.

Typically, the barrier layer 75 is planarized, preferably by CMP, inorder to expose the oxide layer 40 while retaining the barrier layer 75overlying the titanium silicide 67. Preferably, a sufficient depth ofthe barrier layer 75 is retained in order to inhibit silicon diffusionof the polysilicon plug 65 and the titanium silicide layer 67. Thebarrier layer 75 is preferably formed by the layer forming method (i.e.,in the presence of an organometallic catalyst) described above, whereinthe barrier layer 75 is substantially carbon- and oxygen-free. This isadvantageous for two reasons. First, it prevents the poisoning of thehigh dielectric layer by carbon and, second, high capacity devices canbe formed in accordance with the present invention because CVD isparticularly well suited for layer formation on surfaces having highaspect ratios. As shown in FIG. 2, only an upper surface of the barrierlayer 75 is exposed so that the barrier layer sidewalls 80 are protectedby the oxide layer 40.

Preferably, a second relatively thick insulative layer 83 is deposited,patterned and etched to expose at least a portion of the barrier layer75, thus forming an opening (not labeled) thereon. It is not importantthat the opening be precisely aligned with the barrier layer 75.Preferably, the second insulative layer 83 includes an oxide, a nitride,an oxynitride, or mixtures thereof. In formation of any insulative layerherein, formation may be accomplished by depositing two separateinsulative layers. For example, nitride can be deposited and then anoxide can be deposited over the nitride in accordance with the presentinvention.

A layer 85, preferably platinum, is formed by CVD over the secondinsulative layer 83 and exposed portions of the barrier layer 75 to forma lower electrode. It is desirable that the layer 85 is resistant tooxidation to provide a surface for the deposition of a high dielectricconstant material. In addition, the layer 85 protects the top surface ofthe barrier layer 75 from strong oxidizing conditions during depositionof the high dielectric constant material layer 87. Therefore,preferably, platinum, iridium, rhodium, ruthenium, ruthenium oxide,rhodium oxide and iridium oxide can be used as the bottom portion 85 oras one or more layers thereof because it is less likely to oxidizeduring high dielectric constant material deposition and subsequentanneals. In general, an electrode that forms a nonconductive oxide wouldresult in a low dielectric constant layer beneath the high dielectricconstant material, thus negating the advantages provided by the highdielectric constant material.

Following the deposition of the substantially carbon- and oxygen-freelayer 85, and dielectric layer 87, a cell plate electrode layer 88 isprovided to form a storage node capacitor 89, as shown in FIG. 2.

Referring now to FIG. 3, a substantially planar capacitor 120 is shown.The wafer portion of FIG. 2 includes a relatively thin insulative layer100, which has been deposited, patterned and etched such that at least aportion of layer 75 is exposed. A layer of non-oxidizing material formsbottom electrode 105 in accordance with the present invention, asdescribed above with respect to layer 85. A dielectric layer 110 and atop electrode 115 are provided to form the storage node capacitor 120.One skilled in the art will recognize that either one or both of theelectrodes may be formed according to the present invention. Further,the present invention may be used to form one or more layers of a stackforming one or both of the electrodes.

Preferably, for many devices, including those described above, materialssuitable for forming high dielectric constant material layers areselected from the group consisting essentially of Ba_(x)Sr_((1−x))TiO₃[Barium Strontium Titanate or BST], BaTiO₃, SRTiO₃, PbTiO₃, Pb(Zr,Ti)O₃[Lead Zirconium Titanate or PZT], (Pb,La)(Zr,Ti)O₃ [PLZT], (Pb,La)TiO₃[PLT], KNO₃, LiNbO₃, and mixtures thereof. Preferably, cell platelayers, as shown above, are formed with CVD or sputter coating to athickness of about 50 nm to about 200 nm. Preferably, the electrodesinclude a conductive material such as those described above and can beformed in accordance with the present invention.

EXAMPLE

The following example is offered to further illustrate preferredembodiments and techniques. It should be understood, however, that manyvariations and modifications may be made while remaining within thescope of the present invention.

A silicon wafer was placed in a conventional small scale CVD chambermade by Vacuum Products Corp., Hayward, Calif. The organometalliccatalyst was MeCpPtMe₃, and was supplied with a carrier gas of helium at5 SCCM. The precursor, C₆H₈Ru(CO)₃, was supplied with a carrier gas ofhelium at 10 SCCM. The oxidizer, oxygen gas, was supplied at 10 SCCM.The organometallic catalyst was held in a bubbler at a pressure of 10torr and a temperature of 33° C. The precursor was held in a bubbler ata pressure of 10 torr and a temperature of 25° C. The CVD reactionchamber pressure was 5 torr. The deposition temperature at the wafersurface was 315° C. The deposition reaction was carried out for 5minutes.

The silicon wafer having the layer deposited thereon was analyzed usinga PhI 5600 x-ray photo electron spectroscopy (XPS) from PhysicalElectronics, Eden Prairie, Minn.

FIG. 4 is a depth profile generated for a wafer having a layer depositedas described above. The figure shows the composition as a function ofthe depth for the film deposited. FIG. 4 shows that the oxygen contentof the Ru-Pt film is below detection limits of XPS (i.e., less thanabout 0.5% by atomic percent), even though the Ru was co-deposited in anoxygen-containing atmosphere. The carbon levels were also belowdetection limits.

Surprisingly, the ruthenium layer so formed contained no detectablecarbon or oxygen as compared to a layer formed under similar conditionsin the absence of the organometallic catalyst, which formed a rutheniumoxide layer. Further, when a conductive layer was formed by sequentially(as opposed to simultaneously) depositing the a conductive layer on alayer formed from a metal portion of the organometallic catalyst, aconductive metal oxide still formed. Accordingly, it is the depositionof the conductive layer in the presence of the organometallic catalyst(i.e., the simultaneous deposition) that prevents the oxidation of theconductive material during deposition, even in an oxidizing atmosphere.

All patents, patent documents, and publications cited herein areincorporated by reference as if each were individually incorporated byreference. Various modifications and alterations of this invention willbe apparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not limited to the illustrative embodiments set forthherein.

What is claimed is:
 1. A method of optimizing components in a conductivelayer comprising the steps of: (a) forming a conductive layer comprisingthe steps of providing a reactor chamber having a known concentration ofoxygen in an oxidizing atmosphere; providing a substrate having a heatedsurface in the reactor chamber; supplying a fixed amount of a precursorto the reactor chamber; and supplying a fixed amount of anorganometallic catalyst to the reactor chamber, wherein the conductivelayer forms on the heated surface of the substrate; (b) analyzing theconductive layer for component amounts; and (c) repeating the steps (a)and (b) to form one or more additional conductive layers, wherein atleast one of the fixed amount of the organometallic catalyst and theconcentration of oxygen in the oxidizing atmosphere is varied in theformation of each of the one or more additional conductive layers untilcarbon is detected in one of the one or more additional conductivelayers.
 2. The method of claim 1 wherein the fixed amount of theorganometallic catalyst is about 15% by atomic percent and is varied bydecreasing the fixed amount.
 3. The method of claim 1 wherein theorganometallic catalyst comprises a material selected from the groupconsisting essentially of platinum and paladium.
 4. The method of claim1 wherein the known concentration of oxygen in an oxidizing atmosphereis about 30% by atomic percent and is varied by decreasing the knownamount.
 5. The method of claim 1 wherein the precursor comprises amaterial selected from the group consisting essentially of titanium,tantalum, ruthenium, osmium, iron, rhodium, cobalt, nickel, iridium,cerium, tungsten, aluminum, copper, and mixtures thereof.
 6. The methodof claim 1 wherein the conductive layer comprises a material selectedfrom the group consisting essentially of a metal, a metal oxide, a metalnitride and a metal silicide.
 7. The method of claim 1 wherein theconductive layer comprises a substantially carbon- and oxygen-freeconductive layer.
 8. The method of claim 1 wherein the conductive layercomprises a major portion of a material selected from the groupconsisting essentially of titanium, tantalum, ruthenium, osmium, iron,rhodium, cobalt, nickel, iridium, cerium, tungsten, aluminum, copper,and mixtures thereof; and a minor portion of a metal selected from thegroup consisting essentially of platinum and paladium.